It is a poetic fiction about a young American man named Clarel, on pilgrimage through the Holy Land with a cluster of companions who question each other as they pass through Biblical sites.

Melville uses this situation to explore his own spiritual dilemma, his inability to either accept or reject inherited Christian doctrine in the face of Darwin's challenge, and to represent the general theological crisis in the Victorian era.

[1] Clarel is perhaps the longest poem in American literature, stretching to almost 18,000 lines (longer even than European classics such as the Iliad, Aeneid and Paradise Lost).

[2] Clarel, a young American theology student whose Christian beliefs have begun to waver, travels to Jerusalem to renew his faith among some of the sites and scenes of the Old and New Testaments, especially some of the most important places in Jesus's life.

At one point Clarel exchanges looks with Celio, an Italian youth with lumbago who, as a foundling, was reared too protectively by Catholic monks in a Jerusalem monastery but remained very skeptical of Catholicism.

While walking through Jerusalem's streets, Clarel meets Nehemiah, a humble American Christian given to mysticism who hands out proselytizing tracts to pilgrims and tourists.

Vine is an extremely quiet man who seems either to observe completely—his only reaction to some men or situations a strange, silly, or even disturbing look—or to withdraw within himself, distant and lost in thought.

When Vine and Rolfe decide to take a tour of other important sites near Jerusalem—the wilderness where John the Baptist preached and baptized Jesus, the monastery at Mar Saba, and Bethlehem—Clarel wants to accompany them, but he does not wish to leave Ruth.

Jewish customs prohibit Clarel's presence during Ruth and Agar's period of mourning, so the student decides to go on the same pilgrimage Vine and Rolfe will join, confident he will see his beloved when he returns to Jerusalem in a few days.

Other characters appear: Djalea, an emir's son turned tour guide when his people were slaughtered by invaders; Belex, the leader of six armed guards protecting the pilgrims; a wealthy Greek banker and his son-in-law Glaucon; an optimistic Anglican minister named Derwent; an unnamed former elder who has lost the faith; and a Swedish religious seeker and former revolutionist named Mortmain.

Derwent staunchly maintains his faith in biblical accuracy, while Rolfe questions the Bible's basis as factual history even as he acknowledges his desire to believe.

He sees a faint fogbow, which seems to offer hope as it did for Noah, but in the final two lines of Book II, the bow "... showed half spent— / Hovered and trembled, paled away, and— went."

Hawthorne later recorded his concern about Melville, noting how they took a pretty long walk together, and sat down in the hollow among the sand hills (sheltering ourselves from the high, cool wind) and smoked a cigar.

[4] Melville's record of the winter voyage of 1856 (15,000 miles for five months), now known as Journal of a Visit to Europe and the Levant, demonstrates that he did not leave behind his doubts or melancholy.

Melville explored the divide between the preternatural, the religious, and historical reality; he also was influenced by the crisis faced by mid−19th-century Christianity in the wake of the discoveries of Charles Darwin.

Melville saw these scientific developments as simultaneously fascinating (as in the focus on natural history in Moby-Dick) and terrifying, representing a challenge to traditional Christianity that was almost apocalyptic in its significance, especially when combined with the more theological attacks of Protestantism.

[citation needed] As he writes in the troubled and inconclusive Epilogue to Clarel: If Luther's day expand to Darwin's year, Should that exclude the hope — foreclose the fear?

The poem is composed in irregularly rhymed iambic tetrameter (except for the Epilogue), and contains 150 Cantos divided into four books: Jerusalem, The Wilderness, Mar Saba, and Bethlehem.

[5] Similarly, Walter E. Bezanson notes the "curious mixture of the archaic and the contemporary both in language and materials", leading to the inclusion of antique words such as "kern, scrip, carl, tilth and caitiff", alongside modern technical terms taken "from ship and factory, from the laboratory, from trading, seafaring, and war."

The tragedy of modern man, as Melville now viewed it, was one of constriction... Variations from the basic prosodic pattern are so infrequent as to keep the movement along an insistently narrow corridor.

[6] The poem was barely noticed on its original publication, and the few reviews that did appear showed that mainstream critical taste in the United States leant towards the polished, genteel lines of poets such as Henry Wadsworth Longfellow and James Russell Lowell.

The Independent called it a "vast work... destitute of interest or metrical skill", and Lippincott's Magazine claimed that there were "not six lines of genuine poetry in it".

He concedes that present day readers may be "baffled" by the poetic style, but "[o]nce we face up to the idea that Melville's poetry is not an extension of the lyric vein of his famous novels," we can accept that "essentially he was drawn to a non-lyrical, even harsh, prosodic line.

Frank Jewett Mather called it "America's best example of Victorian faith-doubt literature", and Raymond Weaver declared that it contained "more irony, vividness and intellect than almost all the contemporary poets put together."

In 1924, amid the rising tide of literary modernism, the British critic John Middleton Murry approvingly noted the "compressed and craggy" quality of Melville's poetic line, and the French critic Jean Simon found "an extraordinary revelation of a tormented soul"[9] in the work, but noted that the two volumes of the poem represented two essentially distinct spiritual crises.

Seeing the whole work as an obscure elder sibling to T. S. Eliot's The Waste Land, literary scholar Richard Chase has argued that the "sterility of modern life is the central symbolic idea of the poem", and that, after the "extremities of titanism in Pierre", Melville reached the culmination of his later thought: "the core of the high Promethean hero".